EDITORIAL. 
The process of manufacture covers such operations as the follow- 
ing :—Calcination, reduction, crutching, filtering through press, crystal: 
lization, and drying. The rock is placed in a kiln on a bed of coke 
resting on wood, and packed up with alternating layers of coke. Water 
is first driven off, and at 400° ©. the carbonate breaks up. If lime is 
present, it may delay the breaking up, and require a higher temperature. 
At 800° C., however, the reaction is complete. The best type of kiln 
is known as the mixed feed kiln, which is cheaper, both in first cost, 
and in operation expenses. The burnt magnesite—now magnesia Mg.0., 
is drawn from the kilns and passed into a pulverizer. Next follows the 
crutching process. This is carried out in lead-lined vats, into which 
the magnesium sulphate brine from previous lots, and a definite charge 
of H,SO, is gradually run in, and the powdéred magnesia added 
gradually with continuous agitation. The specific gravity of the charge 
is kept as near possible to 1.4. \ This is important, as it determines the 
nature of the salt crystals that form. The temperature is kept about 
65° C. The charge is next pumped through a filter press. This removes 
all insoluble matter, e.g., sand and calcium sulphate,-&e. The clear 
solution is placed in shallow galvanized-iron trays for crystallization. 
In about twelve hours, good crops of crystals are formed, and the 
supernatant liquor is siphoned back to the brine vat. The crystals are 
well drained and dried by a centrifugal drier. This revolves at 1,000 
to 2,000 revolutions per minute for twenty minutes for a charge of 
2 ewt. The crystals are then shovelled on to large drying tables, and a 
further 1 per cent. of moisture is lost. The salt is then ready for 
marketing—if it conforms to the following tests:— 
No impurities of zinc should be present, and no trace of chlorides. 
The salt should be a pure sulphate of magnesium, with very little 
trace of iron compounds. : 
The limit for lead and arsenic is 5 parts per 1,000,000 for each. 
Such is a bare outline of the process, but by the use of up-to-date 
methods of manufacturing, with good labour conditions, and the produc- 
tion of an article that conforms to the high standard of purity of the 
British Pharmacopoia, the locally made salts deserve every success. 
ENGLISH CRITICISM OF AUSTRALIAN LEATHER. 
The following criticism of our leather has been received from the 
Imperial Institute -— 
“ Australian leather is regarded as suitable for certain purposes, ¢.g., 
for the upper leather of boots or for the manufacture of harness, 
saddlery, &c., but it is generally held that it is not, as a rule, sufficiently 
water-resisting to be suitable for general use for soles in wet climates. 
The leather is often too soft and ‘too lightly tanned. It is suggested 
that it could be improved by tanning for a longer time in stronger 
liquors, or by the use of a mixed tannage instead of wattle bark alone. 
It is understood that certain tanners in Australia are now adopting the 
latter plan and are using wattle bark mixed with myrobalans, chestnut 
extract, &c., thereby producing a superior leather, which is satisfactory. 
If the use of mixed tannages were generally adopted in Australia a con- 
siderable improvement in the quality of sole leather would result.” 
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